JP2013154351A - Friction stir welding method, and method for manufacturing underframe of railroad vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction stir welding method capable of prolonging the lifetime of a rotating tool, and a method for manufacturing an underframe of a railroad vehicle.SOLUTION: In the friction stir welding, a probe part 14 of a rotary tool 11 provided with a columnar body part 12 having ceramics and the probe part 14 having projecting ceramics at a center part of a fore end of the body part 12 is pushed into butted parts P of 7N01 materials 2, 2 specified in JIS H 4100, and the butted parts P are joined with each other by rotating the rotary tool 11. The deformation resistance of this material is higher than that of Al alloys such as 6N01 material, and in the friction stir welding of 7N01 material 2 in which the rotary tool 11 is easily worn, the lifetime of the tool is prolonged and the joining at high joining rate becomes possible by using the ceramic-made rotary tool 11 having excellent wear resistance.

Description

  The present invention relates to a friction stir welding method and a manufacturing method of a railcar frame, and more particularly to a friction stir welding and a railcar frame manufacturing method of joining 7N01 materials.

  Aluminum alloys are lighter than materials such as iron and steel, and are therefore often used as structural materials in transportation equipment such as automobiles and railway vehicles. FSW (Friction Stir Welding) is known as one method for joining metal materials such as aluminum alloys. In friction stir welding, a rotating tool is pushed into a contact portion between metal materials and rotated, and the metal materials are joined by plastic flow of the metal portions due to frictional heat. A continuous joint is formed when the rotary tool is moved along the contact portion, and a point joint is formed when the rotary tool is not moved. For example, Patent Document 1 discloses a technique for performing friction stir welding of an aluminum alloy using a tool made of tool steel.

  By the way, in the case of a railway vehicle, 7N01 material, which is an aluminum alloy specified in JIS H4100, is used as a constituent material of a railway vehicle frame. The 7N01 material has high strength and can be recovered to a point close to the strength of the base material by leaving it at room temperature after welding. The current railcar underframe is manufactured by welding workers joining medium thick aluminum alloy members by arc welding.

JP 2002-346770 A

  By the way, in order to reduce welding defects such as blow holes that occur in fusion welding such as arc welding as described above, solid-state bonding such as friction stir welding can be applied to the 7N01 material constituting the railcar frame. . However, since the 7N01 material has higher deformation resistance than an aluminum alloy such as the 6N01 material, it is difficult to apply the friction stir welding particularly to the medium thickness plate. Further, when the friction stir welding is applied to a material having a high deformation resistance, wear of the rotary tool is promoted, and the life of the friction stir welding tool is reduced.

  This invention is made | formed in view of the said subject, and it aims at providing the friction stir welding method and the manufacturing method of a railcar frame which can improve the lifetime of a rotary tool.

  The present invention provides a rotary tool having a cylindrical main body portion having ceramics and a probe portion having ceramics protruding from the center of the tip of the main body portion at a contact portion between 7N01 materials defined in JIS H4100. This is a friction stir welding method in which a contact portion is joined by pushing a probe portion and rotating a rotary tool.

  According to this configuration, a ceramic rotary tool having excellent wear resistance is used in friction stir welding of 7N01 material, which has high deformation resistance compared to an Al alloy such as 6N01 material and is likely to cause wear of the rotary tool. As a result, the tool life is extended and bonding at a high bonding speed becomes possible.

  In this case, the 7N01 material is a plate material having a thickness t (mm), and the peripheral portion at the front end of the main body portion first contacts the surface of the 7N01 material plate material at the contact portion between the end portions of the 7N01 material plate material. A probe part of a rotary tool in which the length from the part to the tip of the probe part along the rotation axis of the main body part is a probe length p (mm) and satisfies t−0.2 (mm) <p ≦ t. It is preferable to push in.

  According to this configuration, when the friction stir welding of the 7N01 material is performed, the clearance between the surface opposite to the side where the probe portion of the plate material is pushed in and the tip of the probe portion is maintained regardless of the thickness of the 7N01 material. It is joined while being kept in the optimum range. For this reason, welding defects such as kissing bonds can be prevented. In addition, when the backing material is supported on the surface of the contact portion opposite to the side where the probe portion is pushed in to support the contact portion, the tip of the probe portion is prevented from contacting the backing material. be able to.

Also, ceramics suitably comprises any the _Si 3 _{N 4} and _Al 2 _{O 3.}

According to this configuration, by using any of Si ₃ N ₄ and Al ₂ O ₃ as ceramics constituting the rotary tool, the rotary tool can be made highly wear-resistant and inexpensive.

  Moreover, this invention is a manufacturing method of the rail vehicle frame which joins 7N01 material by the friction stir welding method of the said invention, and manufactures the rail vehicle frame containing 7N01 material.

  According to this configuration, the railcar frame including the 7N01 material can be manufactured by friction stir welding. For this reason, it is possible to manufacture a railcar frame with high reliability with few welding defects such as blow holes. In addition, the friction stir welding can be automatically welded by controlling the welding speed, the rotational speed of the rotary tool, and the like. Therefore, unlike the conventional arc welding construction, the joining quality is not affected by the skill of the welding worker, and the joining with stable and high joining quality is possible.

  According to the friction stir welding method of the present invention, the tool life is extended, and welding at a high welding speed is possible. In addition, according to the method for manufacturing a railcar frame according to the present invention, it is possible to manufacture a railcar frame with high reliability with few welding defects such as blowholes, and it is possible to bond with stable and high joint quality. Become.

It is a figure which shows the outline of the friction stir welding apparatus to which one Embodiment of the rotary tool which concerns on this invention is applied. It is a side view of the rotation tool shown in FIG. FIG. 3 is an enlarged view around the probe in FIG. 2. FIG. 2 is a perspective view showing a rail and a contact plate of a railcar frame manufactured by friction stir welding by the friction stir welding apparatus shown in FIG. 1. FIG. 5 is an enlarged cross-sectional view of the vicinity of a contact plate taken along line VV in FIG. It is a figure which shows the outline of the modification of the friction stir welding apparatus to which one Embodiment of the rotary tool which concerns on this invention is applied. It is a figure which shows the outline of another modification of the friction stir welding apparatus to which one Embodiment of the rotary tool which concerns on this invention is applied. It is a figure which shows another outline of the friction stir welding apparatus to which one Embodiment of the rotary tool which concerns on this invention is applied. It is a figure which shows an example of the continuous junction part formed using the friction stir welding apparatus shown in FIG. It is a graph which shows the mechanical characteristic of the joint joint formed using the friction stir welding apparatus shown in FIG. It is a figure which shows the test piece after a tension test.

  Hereinafter, with reference to the drawings, preferred embodiments of a friction stir welding method and a railcar frame manufacturing method according to an embodiment of the present invention will be described in detail.

  FIG. 1 is a diagram showing an outline of a friction stir welding apparatus according to the present invention. As shown in FIG. 1, the friction stir welding apparatus 1 is a load control type apparatus that forms a joint 3 along a butted portion P between plate-like 7N01 materials 2 and 2 by using a rotary tool 11. is there. The 7N01 material 2 to be joined is used for, for example, a railcar frame. Examples of the joint location by the railcar frame manufacturing friction stir welding apparatus 1 include a joint portion between a cherry and a backing plate, a joint portion of a reinforcing material, and a joint portion in a vehicle body damper receiver.

  The friction stir welding apparatus 1 includes, for example, a tool holder (not shown) that holds a rotating tool 11, a rotating motor 4 that rotates the rotating tool 11 around the rotation axis A, and the rotating tool 11 that moves along the butted portion P. The moving motor 5 is configured to include a pressing mechanism 6 that presses the rotating tool 11 against the abutting portion, and a controller 7 that controls each motor.

  The tool holder is formed in a substantially cylindrical shape by a ductile material such as metal. The tool holder is inclined about 3 degrees on the opposite side to the joining direction with respect to the normal direction of the 7N01 material 2. An insertion port for the rotary tool 11 is formed at the lower end of the tool holder, and the rotary tool 11 is held by the tool holder by inserting the rotary tool 11 into the insertion port.

Although not shown, a gas supply nozzle that supplies a shielding gas toward the rotary tool 11 is disposed in the vicinity of the tool holder. As the shielding gas, for example, an inert gas such as argon is used. By supplying the shielding gas, grain boundary embrittlement of the joint 3 due to contact with oxygen and nitrogen in the air can be prevented, and a better joint can be obtained. Moreover, it is preferable that the cooling holder for releasing the heat | fever transmitted from the rotary tool 11 during joining is attached to the tool holder.

  As shown in FIG. 1, a backing material 8 may be disposed under the 7N01 materials 2 and 2. The backing material 8 is formed in a plate shape thicker than the 7N01 material 2 by, for example, silicon nitride. The thermal conductivity of the backing material 8 is preferably 15 W / mK or less, for example, and preferably has a load resistance with a bending strength at 900 ° C. of 500 MPa or more.

  When joining using such a friction stir welding apparatus 1, first, the 7N01 materials 2 and 2 are butted together on the backing material 8, and then the rotating tool 11 is arranged above the butted portion P, and the rotating tool 11 probe portions 14 (described later) are pushed into one end of the butted portion P. Then, while supplying the shielding gas, the rotary tool 11 is rotated to the other end of the butted portion P. As a result, frictional heat generated between the probe portion 14 and the metal material 2 enters the abutting portion P, and the joining portion 3 is formed in the abutting portion P by plastic flow due to the frictional heat.

Next, the rotary tool 11 applied to the friction stir welding apparatus 1 will be described in detail. As shown in FIG. 2, the rotary tool 11 includes a main body 12 having a substantially cylindrical shape. The rotary tool 11 is formed from ceramics such as Si ₃ N ₄ and Al ₂ O ₃ . As shown in FIGS. 2 and 3, a shoulder portion 13, a probe portion 14, and a concave portion 15 are provided on the distal end side of the main body portion 12.

  The shoulder portion 13 is a portion that protrudes annularly around the probe portion 14. The cross-sectional shape of the top portion of the shoulder portion 13 is an obtuse angle and a curved surface shape. The outer peripheral portion of the base portion of the shoulder portion 13 is formed by chamfering the distal end periphery of the main body portion 12. Therefore, the shoulder portion diameter φ3 is smaller than the main body portion diameter φ4 of the main body portion 12.

  In this embodiment, since the cross-sectional shape of the top part of the shoulder part 13 becomes an obtuse and curved surface shape, excessive stress is applied to the shoulder part 13 at the time of joining compared with the case where the top part of the shoulder part is a corner part. This prevents the occurrence of cracks without lowering the rotational speed and scanning speed of the rotary tool 11.

  Further, the outer peripheral portion 13 c of the shoulder portion 13 is chamfered at the peripheral edge of the main body portion 12. Thereby, the stress concerning the shoulder part 13 at the time of joining is further relieved, and generation | occurrence | production of a crack can be suppressed more suitably.

  The probe portion 14 has a spherical shape with a curvature radius SR at the top and a weight shape at the base, and is positioned at a substantially central portion on the distal end side of the main body portion 12. The probe portion 14 becomes smaller in diameter as it goes to the tip. Therefore, the probe top diameter φ1 is smaller than the probe base diameter φ2.

  The top portion of the probe portion 14 protrudes from the top portion of the shoulder portion 13 with a length of the probe length p along the rotation axis A of the main body portion 12. That is, the length from the part where the shoulder portion 13 first contacts the surface of the 7N01 material 2 plate to the tip of the probe portion along the rotation axis of the main body portion 12 is the probe length p.

  The concave portion 15 is formed in an annular shape between the base portion of the probe portion 14 and the base portion of the shoulder portion 13. The inclined surface from the top of the shoulder portion 13 to the bottom of the recess 15 has an inclination angle θ with respect to the plane perpendicular to the rotation axis A. The cross-sectional shape of the bottom of the recess 15 is an obtuse and curved surface. An annular concave portion 15 formed by the base portion of the probe portion 14 and the base portion of the shoulder portion 13 is formed around the probe portion 14, and the cross-sectional shape of the concave portion 15 is also an obtuse and curved surface. 15, the 7N01 material 2 can be plastically flowed in a sufficient amount and smoothly. Therefore, in the friction stir welding apparatus 1 to which the rotary tool 11 is applied, the joining speed can be sufficiently improved.

In this embodiment, for example, when performing friction stir welding of 7N01 material 2 having a thickness t = 6 (mm), probe top diameter φ1 = 4 (mm), probe base diameter φ2 = 8 (mm), shoulder diameter φ3 = 16 (mm), body diameter φ4 = 20 (mm), probe length p = 5.9 (mm), tilt angle θ = 10 °, curvature radius SR = 5.4 (mm) . In the present embodiment, the following formula (1) is satisfied regardless of the value of the thickness t of the 7N01 material 2. The probe length p (mm) satisfying the following expression (1) is set according to the thickness t (mm) of the 7N01 material 2, and the clearance between the lower surface of the 7N01 material 2 and the top of the probe portion 14 is within a predetermined range. It is preferable to maintain the high bonding quality.
t−0.2 (mm) <p ≦ t (1)

  The shape parameters of the shoulder portion, the probe portion 14 and the recess portion 15 of the rotary tool 11 can be appropriately changed according to the thickness t of the 7N01 material 2 to be joined. In designing the shape parameters, first, the probe top diameter φ1 and the curvature radius SR of the top of the probe part 14 are determined. The values of the probe top diameter φ1 and the radius of curvature SR are determined by empirical rules, and within the range where the thickness t of the 7N01 material 2 is about several millimeters, for example, as described above, regardless of the material of the 7N01 material 2, Diameter φ1 = 4.0 (mm) and radius of curvature SR = 5.4 (mm).

Further, the shoulder diameter φ3 is obtained from the thickness t of the 7N01 material 2 using the following equation (2). In Equation (2), a known constant is substituted for DB and tB. For example, in the case of the 7N01 material 2, D _B = 15.0 (mm) and t _B = 5.0 (mm).
φ3 = D _B (t / t _B ) ^1/3 (2)

The inclination angle θ is preferably determined in the range of 10 ° to 30 °. After obtaining the shoulder portion diameter φ3, the amount of heat input Q by the rotary tool 11 is obtained using the following equation (3), and the validity of the tool design is confirmed. Expression (3) is a relational expression called Frigard's expression, μ is a friction coefficient, P is a surface pressure (tool load / tool cross-sectional area), and N is a rotation speed. In order to obtain a good joint, it is necessary that the amount of heat input Q applied to the 7N01 material 2 from the rotary tool 11 exceeds the amount of heat necessary for joining in the assumed joining condition range.
Q = (4/3) · πPN (φ3 / 2) ³ (3)

Also, the probe base diameter φ2 is determined. The probe base diameter φ2 is obtained using the following formula (4) constructed by an empirical rule.
φ3: φ2 = 2: 1 (4)

  The main body diameter φ4 is determined according to the mode of the friction stir welding apparatus 1.

  Hereinafter, as an application example of the friction stir welding method of the present embodiment, an example of manufacturing a railcar frame will be described. The railcar frame 100 shown in FIG. 4 is a part to which the weight of the vehicle is added. As shown in FIG. 4, in the railcar frame 100, a contact plate 102 is joined between a pair of maculas 101. The abutting plate 102 is provided with a pair of air spring seats 103 that are round hole portions for installing an air spring. The railcar frame 100 is mainly composed of a medium thickness plate of 7N01 material to ensure strength. For example, the thickness of the macula 101 and the contact plate 102 can be set to 6 (mm).

  As shown in FIG. 5, the friction stir welding method of the present embodiment can be applied to the joint portion 3 between the macula 101 and the contact plate 102. In addition to the above, it can be applied to a joint portion between reinforcement portions, a damper reception between vehicle bodies, end burr reinforcement, etc. The plate thickness of the 7N01 material at the application location is about 5 to 20 (mm). For example, the thickness of the joint portion between the reinforcing portions is about 12 (mm), the thickness of the damper receiver between the vehicle bodies is about 7 (mm) and the thickness of 16 (mm). 6 (mm) and thickness 12 (mm).

In the present embodiment, the rotational tool 11 made of ceramics having excellent wear resistance in the friction stir welding of the 7N01 material 2 that has higher deformation resistance than the Al alloy such as 6N01 material and is likely to cause wear of the rotary tool 11. By using the tool, the tool life is extended, and joining at a high joining speed becomes possible. In particular, in this embodiment, by using any one of Si ₃ N ₄ and Al ₂ O ₃ as ceramics constituting the rotary tool 11, the rotary tool 11 can be made highly wear-resistant and inexpensive.

  In the present embodiment, the probe length p is set so that t−0.2 (mm) <p ≦ t is satisfied with respect to the thickness t (mm) of the 7N01 material 2 and the probe length p (mm). For this reason, when the 7N01 material 2 is subjected to friction stir welding, the clearance between the surface of the plate material opposite to the side where the probe portion 14 is pushed in and the tip of the probe portion 14 regardless of the thickness of the 7N01 material 2. Will be joined while maintaining the optimum range. For this reason, welding defects such as kissing bonds can be prevented. When the backing material 8 is brought into contact with the surface of the butted portion P opposite to the side where the probe portion 14 is pushed in to support the butted portion P, the tip of the probe portion 14 comes into contact with the backing material 8. This can be prevented.

  In the present embodiment, the railcar frame 100 including the 7N01 material 2 can be manufactured by friction stir welding. Therefore, it is possible to manufacture the railcar frame 100 having high reliability with few welding defects such as blow holes. In addition, the friction stir welding can be automatically welded by controlling the welding speed, the rotational speed of the rotary tool, and the like. Therefore, unlike the conventional arc welding construction, the joining quality is not affected by the skill of the welding worker, and the joining with stable and high joining quality is possible.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the embodiment described above, the plate-like backing material 8 is used. However, as shown in FIG. 6, for example, the butted portion P of the 7N01 materials 2 and 2 is formed on the peripheral surface of the columnar backing material 18. The joining portion 3 may be formed by arranging and moving along the butted portion P while synchronizing the position of the rotary tool 11 and the position of the backing material 18. Furthermore, for example, as shown in FIG. 7, the width of the peripheral surface of the columnar backing material 19 may be substantially matched with the main body diameter φ4 of the main body portion 12.

  Also according to such an aspect, the joint portion can be formed with a simple configuration. In the example shown in FIG. 6, even if the probe length p is longer than the thickness t of the 7N01 material 2, scratches due to the probe portion 14 hitting the backing material 8 are less likely to occur. In the example shown in FIG. 7, the backing material 8 can be downsized.

  Further, the present invention can be applied not only to the formation of the continuous joining portion 3, but also to the formation of the point joining portion 20 in the overlapping portion F of the 7N01 materials 2 and 2, as shown in FIG. In this case, a plate-like backing material 8 as shown in FIG. 1 may be used, but a columnar backing material 21 having a diameter substantially coincident with the body portion diameter φ4 of the body portion 12 is used. The overlapping portion F of the 7N01 materials 2 and 2 may be disposed on one end portion in the longitudinal direction of the backing material 21.

(Experimental example)
Hereinafter, the result of measuring the characteristics of the joint 3 by performing friction stir welding of the 7N01 material with the friction stir welding apparatus 1 as shown in FIG. 1 is shown. Friction is applied to the butted portion P between the ends of the plate-like 7N01 materials 2 and 2 having a thickness of 6 (mm) under the conditions of a joining speed of 250 (mm / min) and a rotational speed of the rotary tool 11 of 1000 (rpm). Stir welding was performed. The rotary tool 11 is made of Si ₃ N ₄ and has a probe top diameter φ1 = 4 (mm), a probe base diameter φ2 = 8 (mm), a shoulder diameter φ3 = 16 (mm), and a main body diameter φ4 = 20 ( mm), probe length p = 5.9 (mm), inclination angle θ = 10 °, and curvature radius SR = 5.4 (mm) were used. A continuous joint 3 as shown in FIG. 9 was obtained.

  The 7N01 materials 2 and 2 that were joined were divided into a plurality of pieces perpendicular to the direction in which the joints 3 continued to produce test pieces. A tensile test was performed on the prepared test piece. As shown in FIG. 10, a joint efficiency of 90% of the joint 3 was obtained with respect to the strength of the base material even in the aging material at room temperature for one month that passed for one month at room temperature after joining. Moreover, as shown in FIG. 11, the fracture | rupture position B of the test piece after a tension test is a base material part, and favorable joining quality was obtained.

  DESCRIPTION OF SYMBOLS 1 ... Friction stir welding apparatus, 2 ... 7N01 material, 3 ... Joining part, 8, 18, 19, 21 ... Backing material, 11 ... Rotary tool, 12 ... Main-body part, 13 ... Shoulder part, 14 ... Probe part, 15 DESCRIPTION OF SYMBOLS ... Recessed part, 20 ... Point junction part, 100 ... Railcar frame, 101 ... Macula, 102 ... Contact plate, 103 ... Air spring seat, p ... Probe length, rotating shaft ... A, P ... Butting part (contact part) F: Overlapping part (contact part).

Claims (4)

  The probe portion of the rotary tool provided with a cylindrical main body portion having ceramics and a probe portion having ceramics protruding at the center of the tip of the main body portion at a contact portion between 7N01 materials defined in JIS H 4100 A friction stir welding method in which the contact portion is joined by pushing in and rotating the rotary tool.   The 7N01 material is a plate material having a thickness of t (mm), and the peripheral portion of the tip of the main body portion is first on the surface of the 7N01 material plate material at the contact portion between the end portions of the 7N01 material plate material. The rotating tool satisfying t−0.2 (mm) <p ≦ t, wherein a length from a contact portion to a tip of the probe portion along the rotation axis of the main body portion is a probe length p (mm) The friction stir welding method according to claim 1, wherein the probe portion is pushed. The friction stir welding method according to claim 1 or 2, wherein the ceramic includes any of Si ₃ N ₄ and Al ₂ O ₃ .   The manufacturing method of the rail vehicle frame which joins the said 7N01 material by the friction stir welding method of any one of Claims 1-3, and manufactures the rail vehicle frame containing the said 7N01 material.